The present invention relates to an inkjet head for performing recording operation by jetting ink droplets onto a recording medium and to a method of manufacturing the inkjet head.
Nowadays, inkjet printers for performing recording operation by ejecting ink droplets of water base ink have come into widespread use. In such circumstances, it is strongly desired that the inkjet printers can print and output an image of high quality like a photograph at a high speed.
To cope with this requirement, various technologies have been proposed to improve the quality of an image output by an inkjet printer and to improve the print speed of the inkjet printer. For example, an inkjet head having a water-repellent processed layer disposed in the vicinity of the ink ejection opening of ink ejection nozzles so that ink droplets can be correctly ejected and jetted in desired directions and that an image of high quality can be printed thereby at a high speed.
JP 10-151744 A proposes to coat fluorine polymer in the vicinity of the ink ejection openings of ink ejection nozzles.
FIG. 6 shows an arrangement corresponding to an ink ejection nozzle of an inkjet head in the publication. FIG. 7 shows an enlarged view of a region C shown in FIG. 5.
According to the publication, a heat generation resistor 102 and thin film conductors 104 and 106 are disposed on a substrate 100 and an individual ink path 110 is formed by disposing a partition layer 108 on the substrate 100, and a plate 114 having an inkjet nozzle 112 is bonded on the partition layer 108. Then, a water-repellent processed layer 116 is disposed by coating fluorine polymer in the vicinity of the ejection opening 112a of the inkjet nozzle 112 of the plate 114. In particular, as shown in FIG. 7, water repellency is more improved by making the surface of the water-repellent processed layer 116 into a fine irregular surface 118 of 30 to 60 nm.
In the inkjet head disclosed in the publication, however, the water-repellent processed layer 116 is rubbed with a cleaning blade to clean and remove ink and the like, which is a part of ink droplets jetted onto a recording sheet to be printed thereon, sprung back therefrom and deposited in the vicinity of the ink ejection opening of the ink ejection nozzle 112. Thus, the water-repellent processed layer 116 is worn as the number of times of cleaning increases. Accordingly, when the inkjet printer is used for a long period of time, the water-repellent processed layer 116 is worn out, the plate 114 that is poor in water repellency begins to appear, and a part of ink droplets sprung back from the recording sheet is liable to deposit in the vicinity of the ejection opening of the ink ejection nozzle 112. As a result, a problem arises in that the ejecting directions of ink droplets ejecting from the ink ejection nozzle 112 are disturbed, and thus the ink droplets do not reach the desired positions of the recording sheet and an image of high quality cannot be printed.
This problem arises not only in an inkjet head employing a heating system, in which a heat generation element is used as an actuator for ejecting ink droplets, but also in an inkjet head employing a piezoelectric system in which a piezoelectric device such as a piezoelectric element, and the like is used as an actuator for ejecting ink droplets in the same way.
Accordingly, an object of the present invention, which was made to solve the above problem, is to provide an inkjet head that has a plate through which ink ejection nozzles are disposed to eject ink droplets, is provided with water repellency (ink repellency) to ink droplets at a desired position which is maintained even if the inkjet head is used for a long period of time, and can output a print of high quality, and to provide a method of manufacturing the inkjet head.
The present invetion provides an inkjet head, comprising: an ink ejection unit; and a plate including an ink ejection nozzle disposed in correspondence to the ink ejection unit so that an ink droplet is ejected from the ink ejection nozzle using the ink ejection unit, wherein, fine particles which have a water-repellent function are dispersed in at least a region in proximity to a surface of the plate on an ink ejection side thereof; and wherein the plate is etched using at least two kinds of etching conditions which differ in magnitude relation between an etching rate of the fine particles in the region and an etching rate of the portion of the plate other than the fine particles in the region, and thereby the ink ejection nozzle and the surface of the plate in a vicinity of an ink ejection opening of the ink ejection nozzle are formed.
It is preferable that the plate is arranged such that the fine particles are dispersed in a plate base member, and the plate is etched using an etching condition in which an etching rate of the plate base member is approximately equal to that of the fine particles and an etching condition in which an etching rate of the plate base member is faster than that of the fine particles.
The fine particles having the water-repellent function preferably comprises silicone.
It is also preferable that a fine irregular surface where the fine particles are exposed is formed on the surface of the plate in the vicinity of the ink ejection opening of the ink ejection nozzle.
It is still also preferable that a flat surface with no fine irregular portion is formed on an inner surface of the ink ejection nozzle.
The present invention provides an inkjet head, comprising: an ink ejection unit; and a plate including an ink ejection nozzle disposed in correspondence to the ink ejection unit so that an ink droplet is ejected from the ink ejection nozzle using the ink ejection unit, wherein the plate is arranged such that fine particles, which comprises silicone, are dispersed in a plate base member.
Then, it is preferable that the plate is etched using an etching condition in which an etching rate of the plate base member is approximately equal to that of the fine particles and an etching condition in which an etching rate of the plate base member is faster than that of the fine particles.
The present invention also provides an inkjet head, comprising: an ink ejection unit; and a plate including an ink ejection nozzle disposed in correspondence to the ink ejection unit so that an ink droplet is ejected from the ink ejection nozzle using the ink ejection unit, wherein the plate contains fine particles having a water-repellent function and dispersed therein, and the dispersion density of the fine particles on a back side of the plate opposite to an ink ejection side thereof from which the ink droplet is ejected is lower than that of the fine particles on the ink ejection side.
The present invention still also provides a method of manufacturing an inkjet head comprising an ink ejection unit disposed on a substrate and a plate including an ink ejection nozzle disposed in correspondence to the ink ejection unit and containing fine particles, which have a water-repellent function and are dispersed in at least a region in proximity to a surface of the plate on an ink ejection side thereof, so that an ink droplet is ejected from the ink ejection nozzle using the ink ejection unit, the method comprising the steps of: bonding the plate along the substrate before the ink ejection nozzle is formed through the plate; forming the ink ejection nozzle under a first etching condition in which an etching rate of the fine particles in the region in proximity to the surface and an etching rate of a portion of the plate other than the fine particles in the region have predetermined magnitude relation so that the inner surface of the ink ejection nozzle is arranged as a flat surface; and etching the surface of the plate under a second etching condition which has magnitude relation different from the magnitude relation of the first etching condition so that the surface of the plate in a vicinity of an ink ejection opening of the thus formed ink ejection nozzle is arranged as a fine irregular surface on which the fine particles are exposed.
Then, it is preferable that the first etching condition is such that the etching rate of the fine particles in the region in proximity to the surface is approximately equal to that of the portion of the plate other than the fine particles, and the second etching condition is such that an etching rate of the portion of the plate other than the fine particles is faster than that of the fine particles.
It is also preferable that the ink ejection nozzle is formed by dry etching using a gas containing oxygen and fluorine as a reaction gas, and the surface of the plate is processed by dry etching using an oxygen gas as a reaction gas.